Perishable foods for home, market, catering and restaurant buffets are conventionally chilled by ice or commercially manufactured containers of freezable material, or by refrigeration systems. When the ice melts and the freezable material warms, these cooling media lose their ability to keep foods safe and may render them unsuitable or hazardous for consumption. Refrigeration systems are bulky and costly, requiring condensers, coils and harmful chemicals and, further, must be serviced and maintained. Additionally, they are not easily adapted for portability.
Other foods need to be heated or kept warm for home, market, catering and restaurant buffet service. Conventional sources of heat include flame and electricity, e.g. by use of alcohol-based combustible gels, such as those offered under the tradename STERNO, or by electric hot plates. Flame sources often produce local hot spots and uneven heating and may produce fumes, odors, or other combustion products. The indoor pollution and health risks to food service workers and patrons from these combustion products are beginning to be viewed with concern by those in the industry.
An earlier design of a warm-up and cooling tray for ready-to-serve food is described in U.S. Pat. No. 5,941,077, the disclosure of which is incorporated herein by reference. Such design features two heat-conducting plates in an enclosure, two Peltier elements positioned underneath these plates, a control device for switching the Peltier elements into a plate-cooling or plate-heating mode, as well as selector switches for selecting the desired mode and temperature. U.S. Pat. No. 6,735,958, the disclosure of which is also incorporated by reference, explains that the type of heating and cooling tray disclosed in the '077 patent suffers from a shortcoming in that it cannot produce plate temperatures that lead to ready-to-serve food temperatures in line with current requirements for hygienic considerations. The '958 patent addresses this shortcoming by combining a foil-type heating element with the Peltier elements in order to heat the hot plates of the design “more quickly and/or to higher temperature levels than is possible with Peltier elements alone”, thus achieving temperatures that meet current hygienic requirements. However, by requiring additional heating elements, additional components, monitoring elements, and control circuitry are required to manage the interaction of the disparate type of heating elements, thus raising the costs of such a design.
Consequently, a device that allows for both heating and cooling of a food with a simple set of controls and using only a single-type of temperature adjusting element would be an improvement in the art. The ability to use such a device with pre-existing food service trays, carts and chafing dishes would be an additional improvement. Such a device that is portable and battery powered would be a further improvement.